Many components in gas turbine engines are required to be cooled in order to avoid overheating. In some cases, for example in the case of power electronic components, cooling is achieved by attaching the components to heat sinks.
In many applications in gas turbine engines, the heat sinks are supplied with a fluid, such as fuel or air, which acts as the low temperature reservoir to absorb the heat.
A problem with this arrangement is that in some conditions of use of the engine, the temperature difference between the fluid and the component to be cooled is not large enough to effect sufficient cooling of the component.